Physical and Chemical Changes

Concept of Change Change: the act of altering a substance

Physical Change Physical change: a change that occurs that does not change the identity of the substance. The substance remains the same substance! Melting ice (change in state or phase) Freezing Kool-aid Tearing paper Boiling water (same as melting ice) *Easy to reverse

Chemical Changes Chemical change: a change that occurs causing the identity of the substance to change. A new substance is formed. Burning Digesting food Reacting with other substances A chemical change is called a chemical reaction

Chemical Changes Continued Evidence of a chemical change: Light Heat Production of a gas (bubbles) Colour change Formation of a precipitate (solid material) *Difficult to reverse

Is it Physical or Chemical? Change Physical Chemical Melting cheese Burning wood Milk souring Wadding up paper Bicycle rusting